text: The four JAK family members are:
  * Janus kinase 1 (JAK1)
  * Janus kinase 2 (JAK2)
  * Janus kinase 3 (JAK3)
  * Tyrosine kinase 2 (TYK2)
  Transgenic mice that do not express JAK1 have defective responses to some cytokines, such as interferon-gamma. JAK1 and JAK2 are involved in type II interferon (interferon-gamma) signalling, whereas JAK1 and TYK2 are involved in type I interferon signalling. Mice that do not express TYK2 have defective natural killer cell function.